Normally you would say āa citizen of the worldā in singular.
No, indefinite as in not a particular thing.
Normally itās simple.
Like if you say āIām going to the pond behind the houseā, then I know there is just one pond behind your house and youāre going to that one. Because you used the definite article, the.
If you say āIām going to a pondā, then I donāt know which pond youāre going too (and maybe you donāt either). Because you used an indefinite article (see what I did there?).
Sometimes itās more complicated.
If you say āIām reading a bookā it doesnāt really matter which book, just that youāre reading one. But of course you know which book youāre reading. Youāre just not emphasizing that part. A book = any book, not one particular book.
If you say āIām reading the bookā itās assumed the person youāre talking to knows which book it is, and it is that specific book. For instance you could be reading Alice in Wonderland, your friend knows that and you would be referring to that specific book.
Sometimes you use the definite article even though you donāt have one particular thing in mind. For instance, normally youād say āIām going to the cinemaā whether you know which cinema youāre going to or not. And you would say āI play the violinā even though you can play any violin. This depends on the noun, in this case cinema and violin. Iām not sure what the rules are or if there are any⦠Except that instruments are normally referred to with the definite article. āDo you play the piano?ā is correct. āI always play a guitar at 2 amā sounds strange.
And sometimes you skip the article entirely, as in āIām going to schoolā and āIām going to workā.
Sorry, this is somewhat incorrect. I would know thereās just one pond behind the house because you used the definite article and the noun is in singular form. If it had been in plural form there would be multiple ponds. And with the first sentence (singular) there could be other ponds further away but there is just one which is in the vicinity of the house and behind it
My English isnāt perfect but I think what I wrote here is correct. Now.